Bicycle frame



April 23, 1935. s. s. LEWIS BICYCLE FRAME Filed Aug. 1, 1934 Gear e oilewcls,

Patented Apr. 23, 1935 I 1,998,994

2 UNITED STATES JPAITVENTOFFICEI BICYCLE FRAME George S. Lewis, Evanston, 111., assignor to Battery Patents Corporation, Chicago, 111., a corporation of Illinois Application sum 1,- 1934, Serial No. 737,906

7 Claims. (Cl. 208-95) This invention relates to a bicycle frame or B. The casting C provides centrally a bearing 29 the l k I for the drive-axle and it is equipped with up- An object of the invention is to provide a wardly extending tubular parts 30 and 3|.

bicycle frame of sturdy structure and novel dc- The use of aluminum or aluminum alloys has 5 sign and a lightweight frame consisting of castbeen considered impractical owing to the com- 6 ings and tubes secured together without welding paratively low tensile strength of aluminum or and without bolts, screws, and other like devices. aluminum alloys. To gain the proper strength Other specific objects and advantages will aptherefore, so much metal would be required that pear as the specification proceeds.- the casting would be heavy and unwieldy. By

The invention is illustrated, in its preferred modern processes, aluminum alloys may be heat 10 embodiment, by the accompanying drawing, in treated to give a tensile strength comparable to which- I steel, yet the weight be approximately only one- Figure 1 is a side view in elevation of a bicycle third the weight of a similar casting made of steel. frame embodying my invention; and Fig. 2, a Should, however, the casting after having been broken enlarged sectional view of the cluster cas'theat treated be subjected to awelding orbrazl5 ing, the casting being equipped with a clamping ing heat, the benefit derived from the heat treatcollar. 7 ing process would be lost and the casting would In the illustration, A designates a head castbe no stronger than ordinary commercial alumiing; B, a cluster casting; and C, a bearing castnum. It is apparent therefore that to preserve 2o ing. I t the strength of the heat treated alloy, no fusing The head casting A'is preferably formed of a temperature may be used. I havefound. that a light metal such as duraluminum or other light temperature of 300 F. may be maintained for a and sturdy aluminum alloys. Preferably, the limited time without danger or for a brief period, casting is designed to provide a streamline strucit is possible to go as high as 350 F.

ture providing at its front a tubular part I0 I have found that an aluminum alloyframe of 25 adapted to receive the steering shaft and with a sturdy and simple construction can be produced rearwardly extending tube ll bifurcated at l2. through the use of aluminum castings to which Also, the casting is preferably provided with a tubing is joined by shrinking the castings upon downwardly inclined tube i3 bifurcated at II. the tubing. For example, one of the castings, say

a Merging with the tube I4 is a substantially horicasting A, is heated, preferably in an oil bath, 3o

zontal tube I5. to atemperature of around 300 F. so that the The 'cluster. casting B is provided with a main tubular extensions ll, l3 and I5 expand sufllcientbody portion lfi providing therethrough a central ly to receive connecting tubes which are norbore I1 and having an upwardly extending neck mally too large to be received within the tubular 18. It is preferably formed of the same material extensions. I have found that a satisfactory joint used inthe forming of casting A. Near the lower can be made by having the tubes from 1/ 1000th portion of the neck i8 is an annular recess iii. to about 10/ 1000ths larger than the bore of the The casting B is provided at its forward side with tubular extensions. m atubular extension 20 which is preferably curved By the above method, I have connected the in contour and with a merging tubular extension front casting A to the cluster casting B with the 40 2| just below the tubular extension 20. top tube 32; In the same manner, the cross tube integrally formed with the casting B is a rear- 33 is secured within casting B and casting A. The wardly extending fork portion 22 which is bifurcasting A is secured to the casting 'C by tube 36 cated at 23, which is received within the tubular extension I;

The neck 18 of casting B is slotted at 24' and of casting A and the tubular extension 30 of cast-- 45 a clamp collar 25 i secured to'the upper portion ing 0. The tube as is likewise secured within the of the neck. tubular extension 3| of casting C and the bore The casting C is also preferably formed of ll of casting B. duraluminum or other suitable aluminum alloy., If desired, the tube 35 may be expanded out- The casting is provided with a rearwardly extendwardly at 36 to form an interlocking engagement 50 ing fork portion 26 which is bifurcated at 21, and with the annular recess 19 of fitting B. Also, a which is provided at its rear with a supporting similar interlocking engagement may be made head 28 in whi h t ar n f th r r wh el is between tube 35 and casting C, the expanding tube secured. The head 28 on each of the forks is sebeing extended through tube 35. The tensile cured to the forks of the extension 23 of casting strength of other connections may be likewise 55 increased between the castings by a similar expanding operation, if such .moueaae in tensile strength is desired.

I have found that an extremely sturdy connection can be formed through the expansion of the casting by heat and the subsequent contraction thereof about a tube which is several thousandths reater in diameter than the diameter of the bore in thecasting. Additional strength for the con-' nection can be obtained by chilling the tube while also heating the casting. For example, the tube may be placed in dry ice or any other suitable cooling medium and its temperature reduced until a substantial contraction-of the metal is obtained. When the chilled tube is then placed within the expanded bore of the casting, a substantial shrinking of the bore and expansion of the tube occurs which produces a very tight fit.

The frame may be assembled expeditiously and in a sturdy construction by forcing each of the :tubes into telescoping relation with one of the tubular extensions of the head, cluster or hanger members, none of the parts being heated or chilled. In the pressing operation, the tendency of the aluminum alloy to tear and roughen along the contacting surfaces brings about a practically permanent connection. I

It will be observed that in the design of the tubular extension I l of casting A, tube. and casting B with the tubular extension 20 and the rearward fork extension 23, a substantially bowlike beam is produced with a substantially uniform curve in the central portion of the bow.

- The seat supporting neck l8 of the cluster cast- 3.

ing B is located substantially in the center of the bow structure just described. I find that with this curved construction, a frame of unusual strength is obtained, and that I can use lighter materials than have heretofore been used in these portions of the frame. The structure is so strong that, if desired, the cross tube 33 may be omitted.

The resultant frame is light. in weight, devoid of objectionable welding marks, screw and bolt connections, and is sturdy and substantially integral in construction.

In order to facilitate securing an effective shrunk fit, an aluminum alloy having a high lineal coeihcient ofthermal expansion is used. The particular alloy used, for example, has a coeflicient about two and a half times that of ordinary cast iron, and slightly more than double that of steel. To secure a strong connection if iron were used for the castings in a bicycle frame, it would be necessary to hold the internal diameter of the opening in the casting and the a external diameter of the tube within limits of less than a thousandth of an inch, limits notv economically practicable in bicycle manufacture. The alloy used, on the other hand, permits manufacturing limits several times those possible with cast iron, due to its higher coefiicient of expansion, and has a tensile strength, when properly treated, comparable to that of steel.

While I have described the castings as being secured to the tubes by shrinking the castings thereon, it will be understood that, if desired, the tubes may be expanded within the-castings..or both methods may be used simultaneously; and hi using the words shrunk fit in the appended claims, I intend to cover either or both methods. Itwill also be understood that my invention may be employed by forcing one of the tubes within or into telescoping relation with the tubular extensions of a casting. Such a force fit may be supplemented by passing pins or other connecting means through the telescoping parts.

While the head, cluster and hanger members have been described herein as castings, it will be understood that such members may be made by forging, as would be well understood by men skilled in the art; and in the appended claims where the word "casting is used, it will be understood that this broader meaning of the term is intended.

The foregoing detailed description has been given for cleamess of understanding only, and no unnecessary limitations should be understood therefrom, but the appended claims should be construed as broadly as permissible, in view of the prior art.

I claim:

1. In a bicycle frame of the character set forth, a plurality of castings of aluminum alloy equipped with tubular extensions, and tubes connecting said castings and gripped in telescoping relation with said tubular extensions in a shrunk fit.

2. In a bicycle frame of the character set forth, an aluminum alloy casting provided with a tubular extension, a tube telescopically engaging said extension and frictional gripped thereby, said casting being provided with a recess therein and said tube being expanded adjacent said recess to provide an interlocking shoulder received within said recess.

3. In a bicycle frame of the character set forth, a plurality of castings of aluminum alloy equipped with tubular extensions, and tubes connecting said castings and secured in telescoping relation with said tubular extensions by only the pressure exerted by said tube and tubular extension parts in frictional contact.

4. In a bicycle frame of the character set forth, a plurality of castings of aluminum alloy equipped with tubular extensions, tubes connecting said castings and having their end portions gripped tightly in telescoping relation with said tubular extensions, and locking means engaging said tubes and tubular extensions to prevent the separation thereof.

5. In a bicycle frameof the character set forth, a head member, a cluster member, and a hanger member, said members being formed of aluminum alloy and provided with tubular extensions, tubes telescopically engaging said tubular extensions to connect said members, said tubes and tubular extensions being held together by a force fit only.

6. In the method of assembling a bicycle frame having a cluster casting, a hanger casting and a head casting, each casting being of aluminum alloy and provided with integral tubular bosses, and tubes connecting the castings, the step of pressing said connecting tubes into telescoping relation with said bosses under sufficient pressure to form a substantially permanent-tight force fit.

7. In the method of assembling a bicycle frame having a'hanger casting and a head casting, each casting being of aluminum alloy and provided with integral tubular extensions, and tubes connecting the castings, the step of pressing said connecting tubes into telescoping relation with said extensions under suflicient pressure to form a substantially permanent tight force fit.

GEORGE S. LEWIS. 

